Cover for cultivating particularly bananas

ABSTRACT

A cover for cultivating bananas or other plants includes a plastic film having three layers. A central one of the layers is made of an ethylene and vinyl acetate copolymer, and at least one of the layers includes a UV absorber.

FIELD OF THE INVENTION

The invention concerns a cover, principally for growing bananas.

BACKGROUND OF THE INVENTION

There are already covers for sheathing stalks of bananas, consisting ofa plastic film in polythene (polyethylene), that enable protection to beprovided for the stalk of bananas against insects and against therubbing of leaves and fruit due to conditions such as bad weather, dust,etc..

But bananas are also sensitive to ultra-violet "B" (UV "B") radiation(280-320 nm) which results in the appearance of blemishes on thebanana's skin (black marks) and which causes a disappearance of thechlorophyll (chlorosis). Bananas are also sensitive to infrared (heat)which can cause the same symptoms when the temperature of the fruitexceeds 35° C.

A blue colorant (optalocyanyl blue, ultramarine blue) was then proposedwhich, introduced into the polythene sleeves, protects the bananasagainst burns.

However, this blue cover does not allow all the white light to pass andstops a good part of the UV "A", because of its blue colouring.Nevertheless white light and UV "A" are involved in healing injuries dueto UV "B". The wavelengths absorbed by the blue colorant are thoseabsorbed by the chlorophyll and are those that the plant needs. Inaddition, polythene is a material with a negative greenhouse effect thatlets all infrared pass: the bananas are thus heated by day and rapidlycooled by night. An increase in the heat transmitted to the stalk atnight enables growth to be accelerated by favouring reactions in thedark.

SUMMARY OF THE INVENTION

The invention provides a solution to the above problems by proposing acover consisting of a multi-layer, plastic film of the type including anouter layer, a central layer and an inner layer, the central layerincluding an ethylene and vinyl acetate copolymer and at least one ofthe three layers including at least one light stabilising agent andultraviolet absorber, for growing bananas.

According to one characteristic of the cover under the invention, theethylene and vinyl acetate copolymer contains less than 20% by volume,as compared to the total volume of copolymer, of vinyl acetate.

More precisely, the ethylene and vinyl acetate copolymer includesbetween about 9% and about 19% by volume of vinyl acetate as compared tothe total volume the copolymer.

According to a first embodiment of the invention, only the central layercontains the said at least one light stabilising and UV absorbing agent.

According to a second embodiment of the invention, only the outer layercontains the said at least one light stabilising and UV absorbing agent.

According to a third embodiment of the cover of the invention, only theinner layer contains the said at least one light stabilising and UVabsorbing agent.

According to a fourth embodiment of the invention, only the outer andcentral layers contain the said at least one light stabilising and UVabsorbing agent.

According to a firth embodiment of the invention, only the inner andcentral layers contain the said at least one light stabilising and UVabsorbing agent.

Under a sixth method of producing the invention, the three layerscontain the said at least one light stabilising and UV absorbing agent.

According to a sixth embodiment of the invention, the light stabilisingand UV absorbing agent is 2-hydroxy-4-n-octoxy-benzophenone, which isassociated to a light stabilising agent, poly-(N-β-hydroxyethyl-2, 2, 6,6-tetramethyl-4-hydroxy-piperidyl succinate), each in a quantity of 0.1to 2% by volume as compared to the total volume of copolymer.

According to yet another characteristic of the cover of the invention,the central layer consists in addition of a slip agent such as oleamide.

According to still another characteristic of the cover of the invention,the outer layer is composed of a low density, radical polythene, havinga fluidity index less than 1.5 g/cm² /mn and the inner layer is of a lowdensity, radical polythene having a fluidity index greater than 4 g/cm²/mn.

According to an additional characteristic of the cover of the invention,the inner layer contains in addition an anti-condensation agent, such asa mono-oleate glycerol.

In addition, the outer layer contains a slip agent, such as an oleamideand the inner layer a slip agent, such as an amine, and an anti-blockingagent such as synthetic silica.

In all the embodiments of the cover of the invention, each layerindependently from the others constituting the cover has a thickness ofbetween about 5 and about 13 microns.

The cover of the invention consists of a cylinder of about 50 cm indiameter and between about 140 cm and about 160 cm in height, perforatedin its upper part for about 80 cm only.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood and its other aims andadvantages will appear more clearly in the course of the explanatorydescription which will follow and which is made in reference to theschematic drawings appended in which:

FIG. 1 is a view in perspective representing one method of using thecover of the invention.

FIG. 2 is a view of a vertical look at the cover of the invention.

FIG. 3 is a side view of a cover upright according to a preferredembodiment of the invention.

DETAILED DESCRIPTION

The invention proposes a cover consisting of a plastic film withpositive greenhouse effect, i.e. favouring the growth of bananas by anaddition of heat through a reduction in the loss of heat by radiation atnight and which by day allows all visible light and a good part of theUV "A" to pass and which absorbs UV "B" and reflects infrared (between20 and 30%).

Thus a synergetic effect is obtained that enables more rapid growth ofbananas to be obtained and at the same time an increase in the hardnessof the banana's skin.

This is because it will be out of the question to increase the speed ofgrowth of the fruit without giving the skin of the fruit sufficientstrength to accept this growth.

Referring to FIG. 1 which shows a cover under the invention in use, itis seen that cover 1 has an outer surface in contact with the externalenvironment and an inner surface in contact with the stalk of bananas(3).

Cover 1 is fastened by an appropriate means to the trunk of the bananaplant.

Cover 1 consists of a plastic multi-layer film illustrated in FIG. 2.The plastic film is of the type consisting of an outer layer 4, which isthe layer in contact with the external environment, a central layer 5and an inner layer 6 in contact with the stalk of bananas.

Cover 1 of the invention enables more rapid growth of the bananas,growth directly linked to the quantity of heat transmitted to thebananas, by means of the presence of the central layer 5 consisting ofan ethylene and vinyl acetate copolymer that gives the plastic film athermicity between 80% and 70%. The film thus reflects to the banana apart of the infrared re-emitted at night by the fruit while reflectinginfrared by day to the exterior. This supplies an additional quantity ofheat during the night.

The ethylene-vinyl acetate copolymers have adhesive properties that maketheir production difficult when the quantity by volume of vinyl acetate,as compared to the total volume of ethylene-vinyl acetate copolymer,exceeds 20%. It is thus preferred that the film's central layer 5constituting the cover under the invention contains less than 20% byvolume of vinyl acetate.

However, below 9% by volume of vinyl acetate, as compared to the totalvolume of ethylene-vinyl acetate copolymer, the positive greenhouseeffect is lower.

The multi-layer plastic film used in the invention will thus preferablyhave a central layer 5 consisting of an ethylene-vinyl acetate copolymercontaining between about 9% and 19%, by volume as compared to the totalvolume of copolymer, of vinyl acetate.

An addition of extra heat, i.e. a more rapid growth of the fruit, isthus ensured by the central layer of the cover under the inventioncontaining the ethylene of vinyl acetate copolymer described above. Thecentral layer, furthermore, protects by day, from infrared.

In addition, the cover under the invention absorbs harmful UV "B" whileallowing a great part of the white light and UV "A" to pass.

To this end, the central layer of the cover under the invention cancontain an ultraviolet absorbing agent that absorbs a good part of theultraviolet "B" and thus inhibits blemishes due to UV "B". Profitingfrom all visible light wavelengths, the banana can absorb what it needs,the hardness of the skin is then increased, i.e. it has betterresistance to impacts, injuries, the proliferation of various parasitesand fungi.

Any appropriate agent absorbing UV "B" can be used in combination withthe ethylene and vinyl acetate copolymer, a preferred UV "B" absorbingagent is an agent that not only absorbs UV "B" but also enables theethylene and vinyl acetate copolymer to be stabilised to light, i.e.permitting it to keep its mechanical properties in spite of ultravioletradiation, 2-hydroxy-4-n-octoxy-benzophenone. This light stabilising andUV absorbing agent is used to most advantage in combination with anotherlight stabilising agent, poly-(N-β-hydroxyethyl-2, 2, 6,6-tetramethyl-4-hydroxy-piperidyl succinate). Effective and sufficientquantities of the light stabilising and UV absorbing agent and of thelight stabilising agent mentioned above consist of between 0.1 and 2% byvolume for each of the agents as compared to the volume of ethylene andvinyl acetate copolymer.

It is also possible to add to the central layer an oleamide, currentlyused in plastic film technology to give slip qualities to plastic films.

As has already been emphasised, the central layer consists of anethylene and vinyl acetate copolymer with adhesive properties that makesnecessary the presence of an inner layer, in contact with the fruit, inorder to stop the cover in use from adhering to the fruit. The innerlayer should also be transparent to white light and UV "A". It can alsocontain a light stabilising and UV absorbing agent as well as a lightstabilising agent, for example those contained in the central layer andin the same proportions as in the central layer. It should also berelatively soft so that it does not damage the fruit.

In a preferred method of carrying out the invention, the inner layerthus consists of a low density, radical polythene. A preferred polythenehas a fluidity index greater than 4 g/cm² /mn.

Advantageously, the inner layer in addition contains ananti-condensation agent.

The presence of this anti-condensation agent, by altering the film'ssurface tension properties, enables a uniform distribution of water fromcondensation on the film, and hence a better transmission of the visiblespectrum and UV "A".

The anti-condensation agent on the inner surface also ensures an easierchannelling of the water and hence a reduction in the risk of blemishesthough the "magnifying effect". It also reduces the phenomenon ofdroplets on the fruit by enabling the water to channel away more easily.

All of this thus reduces the occurrence of scorching by reflection ofmoisture.

In other respects the presence of moisture on the stalk favours thedevelopment of Deightonella, a fungus harmful to bananas.

The presence of the anti-condensation agent thus also plays a part inthe better growth of the banana and a better hardness of the banana'sskin.

Any appropriate anti-condensation agent can be used in the inner layerbut a preferred anti-condensation agent is mono-oleate glycerol.

The inner layer of the plastic film constituting the cover under theinvention can also contain a slip agent such as amines and an anti-stickagent enabling avoidance of adhesion of the two inner surfaces of thecover under the invention, when stored and thus enabling the cover to beeasily opened for use. A preferred anti-stick agent is synthetic silica.

Again because the ethylene and vinyl acetate copolymer composite of thecentral layer is adhesive, and to give better mechanical properties tothe film forming the cover under the invention, the central layer iscoated with an outer layer, i.e. that in contact with the ambient air,which should also allow white light and UV "A" to pass, as do the otherlayers.

Preferably the outer layer is composed of a low density, radicalpolythene having a fluidity index less than 1.5 g/cm² /mn, so as to givethe correct mechanical properties to the film for the cover under theinvention.

In order to improve the properties of the cover under the invention, theouter layer can also include the same light stabiliser and UV absorberand associated light stabiliser as those included in the central layer,i.e. 2-hydroxy-4-n-octoxy-benzo-phenone associated withpoly-(N-β-hydroxyethyl-2, 2, 6, 6-tetramethyl-4-hydroxy-piperidylsuccinate) and in the same quantities as for the central layer.

Of course any other polymer and/or light stabilising and UV absorbingagents can be used in so far as they have the same function as thepolythene and light stabilising and UV absorbing agents described above.

Optimally, in order to avoid the covers sticking to one another onstorage, the outer film could include a slip agent such as an oleamide.

The film forming the cover for growing bananas under the invention ismade in a manner in itself recognised in the trade, i.e. for example byco-extrusion in three layers. For preference, its production iscontrolled by computer in order to guarantee a stability and consistencyof the thickness of each layer. This guarantees dose rate ofconstituents.

Preferably, the thickness of each layer constituting the film used inthe invention is between about 5 and about 15 microns.

As can be seen in FIG. 3, the covers under the invention will generallyhave the shape of a cylinder, of a diameter φ of about 50 cm and aheight H between about 1.40 m and 1.60 m.

They can be perforated over the totality of their surface but, accordingto a preferred embodiment illustrated in FIG. 3, which shows a side viewof an upright cover under the invention, the cover will only beperforated on its upper part to a height of about 80 cm. This provides a"chimney effect" that favours the evacuation of water to the outside andthus plays a part in reducing the risk of scorching through reflectionof humidity, a magnifying effect and the reduction of risks of chlorosisby reduction of heat in the container during the day (by convection) andalso by a permanent re-balancing of partial pressures of CO₂ and O₂.

According to one specific embodiment of the invention, the perforationswill have a diameter of 8 mm and each perforation will be at a distanced from others of about 6 cm.

So that the invention's aims and advantages are better understood,several embodiments will now be described by way of examples that arepurely illustrative and not limiting.

EXAMPLE 1

Trials were undertaken in Guadeloupe, using the cover under theinvention, and for comparison the cover in blue polythene previouslyused by growers and also using no covers.

During a "June-July-August" growth period we measured the rate of growthof the fruit and hardness modulus of the skins when grown without asleeve, with a sleeve in blue polythene previously used by growers andwith the sleeve under the invention.

In this example, the sleeve under the invention was as follows:

outer layer: thickness between 5 and 15 microns, composed of a lowdensity, radical polythene with a fluidity index less than 1.5 g/cm² /mnand with a light stabiliser and UV absorber:2-hydroxy-4-n-octoxy-benzophenone in an amount of 0.1 to 2% by volume ascompared to the total volume of polythene; and a light stabiliser:poly-(N-β-hydroxyethyl-2, 2, 6, 6-tetramethyl-4-hydroxy-piperidylsuccinate), in an amount of 0.1 to 2% by volume as compared to the totalvolume of polythene.

In addition, it includes an oleamide.

central layer: thickness between 5 and 15 microns, composed of anethylene and vinyl acetate copolymer containing between 9 and 19% byvolume, as compared to the total volume of copolymer, of vinyl acetate,a light stabiliser and UV absorber: 2-hydroxy-4-n-octoxy-benzophenone,in an amount between 0.1 to 2% by volume as compared to the volume ofcopolymer, and a light stabiliser: poly-(N-β-hydroxyethyl-2, 2, 6,6-tetramethyl-4-hydroxy-piperidyl succinate), in an amount between 0.1to 2% by volume as compared to the total volume of copolymer.

In addition, it includes an oleamide.

inner layer: thickness between 5 and 15 microns, composed of a lowdensity, radical polythene with a fluidity index greater than 4 g/cm²/mn and with a light stabiliser and UV absorber:2-hydroxy-4-n-octoxy-benzophenone in an amount between 0.1 to 2% byvolume as compared to the volume of polythene, and a light stabiliser:poly-(N-β-hydroxyethyl-2, 2, 6, 6-tetramethyl-4-hydroxy-piperidylsuccinate), in an amount of 0.1 to 2% by volume as compared to the totalvolume of polythene.

In addition, it contains synthetic SiO₂, amines and mono-oleateglycerol.

Hardness modulus measurements were made by measuring the pressure at thesurface of the skin at a constant penetration speed of 2 mm/s with apellet of 20 mm². Two series of trials were conducted: at an altitude of300 m and at an altitude of 50 m and the bananas were cut at the samegrade (diameter).

Table 1 below gives the results obtained at 300 m altitude and table 2gives the results obtained at 50 m altitude.

                  TABLE 1                                                         ______________________________________                                                without   sleeve of                                                                              sleeve under                                               sleeve    blue     the invention                                      ______________________________________                                        Rate of   0.18        0.22     0.29                                           growth of                                                                     diameter (in                                                                  hardness  1550        1550     1550                                           modulus (in                                                                   g)                                                                            ______________________________________                                    

From the results obtained at 300 m altitude, it can be seen that therate of growth of bananas increases with the use of the cover under theinvention and that the hardness of the skin remains constant. It must benoted here that the skin hardness modulus was already very high at thisaltitude.

                  TABLE 2                                                         ______________________________________                                                without   sleeve of                                                                              sleeve under                                               sleeve    blue     the invention                                      ______________________________________                                        Rate of   --          0.26     0.29                                           growth of                                                                     diameter (in                                                                  hardness  --          1280     1480                                           modulus (in                                                                   g)                                                                            ______________________________________                                    

From the results obtained at 50 m altitude, a lesser increase isobserved in the rate growth of fruit and a steep increase in the skinhardness modulus.

But the fruit's rate of growth is already very substantial on the plainand one of the problems encountered in this area is the low skinhardness modulus of the fruit. Using the cover under the invention thusenables a clear increase in the skin hardness modulus, i.e. solvingproblems encountered at 50 m altitude and in addition increasing thegrowth rate of the fruit.

Generally speaking, from the results obtained in this example, asignificant reduction is seen in the type of difference in the criteriameasured: the hardness modulus tends to become "uniform", between 1450and 1550 g, and the rate of growth increases to 0.29 mm/day.

But, in a more important manner, the cover under the invention can beadapted to different sites where bananas are grown.

This can be done through varying the quantity of UV absorber or by usingits presence or absence in the various layers composing the cover underthe invention.

This is because the UV absorber used in the invention transforms UV "B"into heat, i.e. into infrared and the copolymer making up the centrallayer in vinyl-ethylene acetate reflects this infrared.

This means that according to the sunnyness of the day, i.e. the amountof sunshine and the period of sunshine, these rates and periodsthemselves depending on season and altitude, for example the compositionof the cover under the invention can be adapted to obtain a better fruitgrowth rate increase/skin hardness increase ratio.

For example, it was seen in example 1 that in the area called "theplain", i.e. at an altitude of less than 100 m, the growth rate of thefruit is already substantial and that the problem encountered is the oneof a low skin hardness of the fruit. Consequently in this area one willseek more to promote an increase in skin hardness than fruit growth. Theadditional supply of heat due to the transformation of UV "B" into heatis thus not necessary.

In such a case a cover under the invention can be chosen that containsthe light stabilising and UV absorbing agent (with the associated lightstabilising agent) only in the central layer and/or the outer layer.

With this configuration UV "B" is absorbed and transformed into heat(IR) when it passes through the outer layer. And the vinylacetate-ethylene copolymer contained in the central layer reflects thisadditional supply of heat to the exterior, by day.

Of course at night the infrared emitted by the fruit will be reflectedback to the fruit by the central layer containing the ethylene-vinylacetate copolymer.

However, in the area called "mountain", i.e. at an altitude of more than100 m, the hardness of the skin is already satisfactory but, on theother hand, the growth rate of the fruit is low. In this instance it isthus very advantageous to have an additional supply of heat due to thetransformation of UV "B" into heat (IR). It is then especiallypreferable to use, in mountain areas, a cover containing the lightstabilising and UV absorbing agent (with the associated lightstabilising agent) only in the inner layer and/or the central layer.

In this configuration UV "B" rays cross the central layer, aretransformed into heat (IR) in the central layer and/or the inner layerand the presence of the vinyl acetate-ethylene copolymer in the centrallayer will reflect, by day, this supply of additional heat to the fruit.

Summarising, the combination of a central layer consisting of a materialwith positive greenhouse effect, here ethylene-vinyl acetate copolymer,with a UV absorber contained either in the three layers forming thecover under the invention, or in one of these layers alone, enables thecover under the invention to be adapted to all of the climate situationsencountered in growing the fruit.

In the case where the cover under the invention contains a lightstabilising and UV absorbing agent (with the associated lightstabilising agent) only in the central layer, when appropriate withregard to climate conditions, this cover will present the advantage thatthe inner layer, i.e. the one in contact with the fruit, will serve asan "insulating" layer as compared to the central layer in ethylene-vinylacetate copolymer, which will itself be warm.

The following example illustrates other advantages of the invention.

EXAMPLE 2

Trials were undertaken on plants (first cycle) that are in plantationsrecognised as fragile, in two places, namely on the plain (altitude 30m) and in the mountains (altitude 250 m).

The growing period was from September to December which is the time ofyear the most favourable for growing bananas, but in that year, therewere problems of drought, particularly on the plain.

Observations were made by comparing certain criteria between stalksgrown under a blue sleeve as previously used and stalks grown under asleeve in the invention for the same flower-cut interval (FCI). Theflower-cut interval is the period of time that elapses between floweringof the banana plant and cutting the bananas.

The criteria measured and results obtained are given below in Table 3.

In the table, the difference in grade represents the difference in thediameter of the fruit measured by a calliper gauge between fruit grownwith the previously used blue cover and with the cover under theinvention.

In similar fashion, the difference in length was measured of fruitobtained with the previously used blue cover and with the cover underthe invention. The differences in weight, hardness and firmness of fruitobtained with the previously used blue cover and with the cover underthe invention are also given.

On the plain, the cover under the invention contained the lightstabilising and UV absorbing agent and the associated light stabilisingagent described in Example 1 only in the central layer and outer layerwhereas at altitude, the cover under the invention contained the lightstabilising and UV absorbing agent and the associated light stabilisingagent described in Example 1 only in the central layer and inner layer.

The invention's other characteristics were identical to those for thecover used in Example 1.

                  TABLE 3                                                         ______________________________________                                               Growing on the                                                                              Growing at                                                      plain         altitude                                                        75 day FCI    86 day FCI                                               ______________________________________                                        difference in                                                                          +1 nm           +1.5 mn                                              grade                                                                         difference in                                                                          Hand 1 = +1 cm  Hand 1 = +1.4 cm                                     length   Hand 7 = +0.3 cm                                                                              Hand 7 = +0.8 cm                                     difference in                                                                          Hand 1 = +22 g/finger                                                                         Hand 1 = +19 g/finger                                weight   Hand 6 + 9 g/finger                                                                           Hand 6 = +12 g/finger                                hardness Cover under     Cover under                                                   the invention > the invention >                                               blue cover      blue cover                                           firmness Cover under     Cover under                                                   the invention > the invention >                                               blue cover      blue cover                                           ______________________________________                                    

Also, with the cover under the invention, photosynthesis activity ismore substantial than with the blue polythene covers.

The fruit's pistils (tip of the banana's male inflorescence) disappearedon the stalks covered with the cover under the invention. Removingpistils is a paid task on banana plantations. Absence of the need toremove pistils thus results in enormous savings.

The bananas lengthen more rapidly which allows a greater opening of thehands at the bottom of the stalk and thus avoids damage of one hand byanother. Waste of one hand/stalk (i.e. about 1 kg) is estimated due tothis type of damage.

Although ripening more quickly, physiologically the bananas are younger.This enables:

either the bananas to be left longer on the plant and thus heavier fruitto be obtained (+11% in weight per week),

or to benefit from the additional time to allow the bananas to travelwithout problems of premature ripening

or a combination of both advantages.

Of course the invention is not limited to the embodiments described andillustrated which have only been given by way of examples.

Hence any plastic film or combination of films with positive greenhouseeffect, absorbing UV "B", allowing UV "A" and white light to pass couldbe used to make a cover under the invention.

In addition, the cover under the invention could be used for growingfruit other than bananas, if appropriate.

This is the case, in general, for any growing system having asignificant photosynthesis activity and of a size compatible with theuse of plastic covers. Mentionable in particular are vine stocks, stalksof dates, some cucurbita (gourd family), any fruit on stalks or inbunches and any small sized bushes.

Furthermore, the cover under the invention should have a very effectiverole in stimulating the growth of offshoots on banana plants when placedon the offshoots.

In all these applications, only the form of the cover changes and thevarious concentrations.

Of course, the cover under the invention could also have otherdimensions than those described here.

On the contrary, the invention comprises all the technical equivalentsfor the means described as well as their combinations if they are donein the same spirit.

I claim:
 1. A cover for growing plants comprising a multi-layer plasticfilm including an outer layer, a central layer and an inner layer, thecentral layer comprising an ethylene and vinyl acetate copolymer and atleast one of the layers comprising at least one light stabilizing andultraviolet absorbing agent.
 2. A cover as claimed in claim 1 whereinthe ethylene and vinyl acetate copolymer comprises less than 20% byvolume of vinyl acetate as compared to the total volume of thecopolymer.
 3. A cover as claimed in claim 1 wherein the ethylene andvinyl acetate copolymer comprises between about 9% and about 19% byvolume of vinyl acetate as compared to the total volume of thecopolymer.
 4. A cover as claimed in claim 1 wherein the lightstabilizing and ultraviolet absorbing agent comprises2-hydroxy-4-n-octoxy-benzophenone, the cover further comprisingpoly-(N-β-hydroxyethyl-2,2,6,6-tetramethyl-4-hydroxy-piperidylsuccinate) as a light stabilizing agent, each in an amount of 0.1 to 2%by volume as compared to the total volume of the copolymer.
 5. A coveras claimed in claim 1 wherein each of the three layers comprises atleast one light stabilizing and UV absorbing agent.
 6. A cover asclaimed in claim 1 wherein only the central layer comprises the at leastone light stabilizing and UV absorbing agent.
 7. A cover as claimed inclaim 1 wherein only the outer layer comprises the at least one lightstabilizing and UV absorbing agent.
 8. A cover as claimed in claim 1wherein only the inner layer comprises the at least one lightstabilizing and UV absorbing agent.
 9. A cover as claimed in claim 1wherein the central layer and outer layer each comprise the at least onelight stabilizing and UV absorbing agent.
 10. A cover as claimed inclaim 1 wherein the central layer and inner layer each comprise the atleast one light stabilizing and UV absorbing agent.
 11. A cover asclaimed in claim 1 wherein the inner layer further comprises ananti-condensation agent.
 12. A cover as claimed in claim 1 wherein thecentral layer further comprises a slip agent.
 13. A cover as claimed inclaim 1 wherein the outer layer comprises a low density, radicalpolyethylene having a fluidity index less than about 1.5 g/cm² /mn andthe inner layer comprises a low density, radical polyethylene having afluidity index greater than about 4 g/cm² /mn.
 14. A cover as claimed inclaim 1 wherein the outer layer further comprises a slip agent, and theinner layer further comprises a slip agent and an anti-stick agent. 15.A cover as claimed in claim 1 wherein each layer of the multi-layerplastic film has a thickness between about 5 and about 15 micrometers.16. A cover as claimed in claim 1 wherein the cover is cylindrical witha diameter of about 50 cm, has a height of between about 140 cm and 160cm, and is perforated only on an upper part thereof over about 80 cm.17. A method of using the cover according to claim 1 for growing vines,dates, or cucurbita.
 18. A method of using the cover according to claim1 to accelerate growth of offshoots from banana plants.
 19. A cover asclaimed in claim 1 wherein the inner layer comprises ananti-condensation agent, the anti-condensation agent comprisingmono-oleate glycerol.
 20. A cover as claimed in claim 1 wherein thecentral layer further comprises a slip agent, the slip agent comprisingoleamide.